Geometry Nodes: Make displaying "Manage" panel optional

Often displaying the "Manage" panel is not very useful, or at least it
isn't worth taking up the screen real-estate. This commit adds an option
for showing the panel in the modifier, and adds an option to the node
group which is used to initialize the modifier option when creating a
modifier for a node group asset.

Pull Request: https://projects.blender.org/blender/blender/pulls/146775

source/blender/modifiers/intern/MOD_ui_common.cc

@@ -302,6 +302,7 @@ static void modifier_ops_extra_draw(bContext *C, uiLayout *layout, void *md_v)
                         blender::wm::OpCallContext::InvokeDefault,
                         UI_ITEM_NONE);
     layout->prop(&ptr, "show_group_selector", UI_ITEM_NONE, std::nullopt, ICON_NONE);
+    layout->prop(&ptr, "show_manage_panel", UI_ITEM_NONE, std::nullopt, ICON_NONE);
   }
 }